scholarly journals Gas flow permeability and gas pressures in stilt roots of Red Mangrove (Rhizophora mangle L.)

2021 ◽  
Author(s):  
Dennis G Searcy
Keyword(s):  
Gas Flow ◽  
Pressure Gauge ◽  
Rhizophora Mangle ◽  
The Core ◽  
Red Mangrove ◽  
Measured Flow ◽  
Impermeable Layer ◽  
Flow Pathways ◽  
Stilt Root ◽  
Gas Pressures

The Red Mangrove (Rhizophora mangle) is typically rooted in anoxic mud conditions that require special adaptations for root oxygenation. Each plant has multiple "stilt roots" that descend from upper branches and end in roots buried the mud. In cross section each stilt root consists of a core of porous aerenchyma surrounded by an impermeable layer of xylem, and outside the xylem there is a second layer aerenchyma. Oxygen must be provided to the mud roots through the aerenchyma either by diffusion or by gas flow, where the separate layers could provide up- and down-flow pathways. To test whether the stilt root's properties were consistent with gas flow, conductivities were measured. A technique was developed that measured flow conductivities in S.I. scientific units without using a flow meter and a calibrated pressure gauge. The core aerenchyma was more permeable to gas flow than any other plant tissue, except for those stems that are hollow tubes. Because there was little lateral leakage from the core aerenchyma, it had pipe-like properties. In the outer aerenchyma gas conductivity was high, and gas flowed easily through large lenticels on the surface of the stilt root. To complete the calculations, gas pressures in the stilt roots were measured. The calculated gas flow rates through mud roots was not sufficient to supply O2 for root respiration, suggesting that diffusion may be the more important mechanism for these plants.

Pressure Assisted Sintering of an Aluminium Alloy

2009 ◽  
Vol 618-619 ◽  
pp. 627-630
Author(s):  
Stephen J. Bonner ◽  
Graham B. Schaffer ◽  
Ji Yong Yao
Keyword(s):  
Aluminium Alloy ◽  
Gas Flow ◽  
Isothermal Holding ◽  
Horizontal Tube ◽  
Elevated Pressure ◽  
Nitrogen Pressure ◽  
Gas Pressure ◽  
Densification Rate ◽  
Conventional Press ◽  
Gas Pressures

An aluminium alloy was sintered using a conventional press and sinter process, at various gas pressures, to observe the effect of sintering gas pressure on the densification rate. Compacts of aluminium alloy 2712 (Al-3.8Cu-1Mg-0.7Si-0.1Sn) were prepared from elemental powders and sintered in a horizontal tube furnace under nitrogen or argon at 590°C for up to 60 minutes, and air cooled. The gas flow was adjusted to achieve specific gas pressures in the furnace. It has been found that increasing the nitrogen pressure at the start of the isothermal holding stage to 160kPa increased the densification rate compared to standard atmospheric pressure sintering. Increasing the nitrogen pressure further, up to 600kPa, had no additional benefit. The densification rate was increased significantly by increasing the gas pressure to 600kPa during both heating and isothermal holding. Under argon the elevated pressure did not increase the densification rate. Results seem to suggest that the beneficial effect of the elevated pressure on the rate of densification is related to nitride formation.

Behavior of Radial Incompressible Flow in Pneumatic Dimensional Control Systems

2003 ◽  
Vol 125 (5) ◽  
pp. 843-850 ◽  
Author(s):  
G. Roy ◽  
D. Vo-Ngoc ◽  
D. N. Nguyen ◽  
P. Florent
Keyword(s):  
Gas Flow ◽  
Flow Behavior ◽  
Pressure Gauge ◽  
Axisymmetric Flow ◽  
Low Pressure ◽  
Industrial Applications ◽  
Nozzle Geometry ◽  
Machined Surface ◽  
Flow Area ◽  
Simpler Algorithm

The application of pneumatic metrology to control dimensional accuracy on machined parts is based on the measurement of gas flow resistance through a restricted section formed by a jet orifice placed at a small distance away from a machined surface. The backpressure, which is sensed and indicated by a pressure gauge, is calibrated to measure dimensional variations. It has been found that in some typical industrial applications, the nozzles are subject to fouling, e.g., dirt and oil deposits accumulate on their frontal areas, thus requiring more frequent calibration of the apparatus for reliable service. In this paper, a numerical and experimental analysis of the flow behavior in the region between an injection nozzle and a flat surface is presented. The analysis is based on the steady-state axisymmetric flow of an incompressible fluid. The governing equations, coupled with the appropriate boundary conditions, are solved using the SIMPLER algorithm. Results have shown that for the standard nozzle geometry used in industrial applications, an annular low-pressure separated flow area was found to exist near the frontal surface of the nozzle. The existence of this area is believed to be the cause of the nozzle fouling problem. A study of various alternate nozzle geometries has shown that this low-pressure recirculation area can be eliminated quite readily. Well-designed chamfered, rounded, and reduced frontal area nozzles have all reduced or eliminated the separated recirculation flow area. It has been noted, however, that rounded nozzles may adversely cause a reduction in apparatus sensitivity.

Fungi Associated with the Roots of Red Mangrove, Rhizophora mangle

Mycologia ◽  
1973 ◽  
Vol 65 (4) ◽  
pp. 894 ◽  
Author(s):  
Benny K. H. Lee ◽  
Gladys E. Baker
Keyword(s):  
Rhizophora Mangle ◽  
Red Mangrove

scholarly journals Impact of Heterogeneity on the Transient Gas Flow Process in Tight Rock

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3559 ◽  
Author(s):  
Jia ◽  
Tsau ◽  
Barati ◽  
Zhang
Keyword(s):  
History Matching ◽  
Gas Flow ◽  
Preferential Flow ◽  
Early Stage ◽  
Ideal Gas ◽  
Flow Path ◽  
Flow Process ◽  
The Core ◽  
Porosity And Permeability ◽  
Preferential Flow Path

There exits a great challenge to evaluate the flow properties of tight porous media even at the core scale. A pulse-decay experiment is routinely used to measure the petrophysical properties of tight cores including permeability and porosity. In this study, 5 sets of pulse-decay experiments are performed on a tight heterogeneous core by flowing nitrogen in the forward and backward directions under different pressures under pore pressures approximately from 100 psi to 300 psi. Permeability values from history matching are from about 300 nD to 600 nD which shows a good linear relationship with the inverse of pore pressure. A preferential flow path is found even when the microcrack is absent. The preferential path causes different porosity values using differential initial upstream and downstream pressure. In addition, the porosity values calculated based on the forward and backward flow directions are also different, and the values are about 1.0% and 2.3%, respectively, which is the primary novelty of this study. The core heterogeneity effect significantly affects the very early stage of pressure responses in both the upstream and downstream but the permeability values are very close in the late-stage experiment. We proposed that that there are two reasons for the preferential flow path: the Joule–Thomson effect for non-ideal gas and the core heterogeneity effect. Based on the finding of this study, we suggest that very early pressure response in a pulse-decay experiment should be closely examined to identify the preferential flow path, and failure to identify the preferential flow path leads to significant porosity and permeability underestimation.

Reverse Flow Pressure Limiting Aperture

2000 ◽  
Vol 6 (1) ◽  
pp. 21-30 ◽  
Author(s):  
Gerasimos D. Danilatos
Keyword(s):  
Pressure Difference ◽  
Gas Flow ◽  
Reverse Flow ◽  
Gas Jet ◽  
The Third ◽  
The Core ◽  
Annular Aperture ◽  
Flow Through ◽  
Flow Pressure ◽  
Gas Molecules

The reverse flow pressure limiting aperture is a device that creates and sustains a substantial gas pressure difference between two chambers connected via an aperture. The aperture is surrounded by an annular orifice leading to a third chamber. The third chamber is maintained at a relatively high pressure that forces gas to flow through the annular aperture into the first of said two chambers. The ensuing gas flow develops into a supersonic annular gas jet, the core of which is coaxial with the central aperture. A pumping action is created at the core of the jet and any gas molecules leaking through the aperture from the second chamber are entrained and forced into the first chamber, thus creating a substantial pressure difference between the first and second chamber.

Studies on the Growth of Red Mangrove (Rhizophora mangle L.) 3. Phenology of the Shoot

Biotropica ◽  
1971 ◽  
Vol 3 (2) ◽  
pp. 109 ◽  
Author(s):  
A. M. Gill ◽  
P. B. Tomlinson
Keyword(s):  
Rhizophora Mangle ◽  
Red Mangrove

Investigation of Annular Jet Flows in a Subsonic Air-Air Ejector With Multi-Ring Entraining Diffuser

2015 ◽  
Author(s):  
A. Namet-Allah ◽  
A. M. Birk
Keyword(s):  
Boundary Conditions ◽  
Turbulence Model ◽  
Nozzle Exit ◽  
Turbulence Models ◽  
Domain Size ◽  
Pressure Recovery ◽  
Cfd Simulations ◽  
The Core ◽  
Measured Flow ◽  
Air Ejector

The current paper presents a cold flow simulation study of a low Mach number air-air ejector with a four ring entraining diffuser that is used in a variety of applications including infrared (IR) suppression of exhaust from helicopters and fixed wing aircraft. The main objectives of this investigation were to identify key issues that must be addressed in successful CFD modelling of such devices, and recognize opportunities to improve the performance of these devices. Two-dimensional CFD simulations were carried out using commercial software, Ansys14. Studies of mesh and domain size sensitivity were made to ensure the CFD results were independent of both factors. A turbulence model independence study using k-ε, k-ω and RSM turbulence models was performed to figure out the appropriate turbulence model that produced the best agreement with the experimental data for several of ejector performance criteria. The measured flow properties in the annulus were used as input boundary conditions for the CFD simulations. However, in the comprehensive turbulence model study, the measured flow parameters at the nozzle exit were also applied as inlet boundary conditions for the CFD simulations. The measured flow velocity at the nozzle exit, at one centerline section inside the mixing tube and at the diffuser exit and the system pressure recovery were compared with the CFD predictions. The ejector pumping ratios, back pressure coefficient and diffuser gap velocities were also compared. It was found that the RANS-based CFD predictions were sensitive to the changes in the ejector domain size, mesh refinement and inlet boundary condition locations. With the annulus inlet boundary conditions, the tested turbulence models under predicted the size of the core separation downstream of the system, back pressure, pumping ratio and pressure recovery in the mixing tube and diffuser. However, the ability of the RNG turbulence model to predict the ejector performance parameters was better than that of the other turbulence models at all inlet flow conditions. Nevertheless, applying the inlet boundary conditions at the nozzle exit enhanced the capability of the RANS-based turbulence model particularly in predicting the ejector pumping ratios, pressure recovery and the size of the core separation. Finally, the acceptable agreement between the experimental data and the CFD predictions provides a valid tool to continue improving these devices using CFD techniques.

Effect of environment and gibberellins on the early growth and development of the red mangrove, Rhizophora mangle L.

1996 ◽  
Vol 20 (3) ◽  
pp. 215-223 ◽  
Author(s):  
S. M. Smith ◽  
Y. Y. Yang ◽  
Y. Kamiya ◽  
S. C. Snedaker
Keyword(s):  
Growth And Development ◽  
Rhizophora Mangle ◽  
Early Growth ◽  
Red Mangrove
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